Drawing press pressure control

ABSTRACT

A mechanism for controlling the pressure resisting the stroke of a drawing press consists primarily of two fluid actuated control pistons. The drawing stroke is first resisted by only one of the pistons and then, after a predetermined amount of movement, is resisted by both pistons. The time which the stroke is resisted only by the first piston can be varied according to the physical properties of the material being drawn so that undesirable distortions in the article being manufactured are avoided.

United States Patent Clendenin et al.

1451 Apr. 4, 1972 41 DRAWING PRESS PRESSURE CONTROL [72] Inventors: William H. Clendenin, Massillon; Thomas B. Paumier, Canton, both of Ohio [73] Assignee; Paumier, lnc., Canton, Ohio [22] Filed: July 6, 1970 21 Appl. No.: 52,167

- 267/119 51] 1111. C1 ..F0lb 7 00 [58] Field of Search ..92/61, 65, 62, 85, 151, 134;

56 References Cited UNITED STATES PATENTS 1,602,411 10/1926 Rode ..267/119 )4 1,773,439 8/1930 .Rode ..267/1l9X 2,584,339 2/1952 Georgeff ..267/119 3,130,963 4/1964 Stegner ..267/1 19 3,447,795 6/1969 Vickers..... ..267/1 19 3,451,667 6/1969 Anderson ..267/1 19 I Primary Examiner-Edgar W. Geoghegan Assistant Examiner,l.eslie J. Payne Attorney-Hamilton, Renner & Kenner [571 ABSTRACT A mechanism for controlling the pressure resisting the stroke ofa drawing press consists primarily of two fluid actuated control pistons. The drawing stroke is first resisted by only one of the pistons and then, after a predetermined amount of movement, is resisted by both pistons. The time which the stroke is resisted only by the first piston can be varied according to the physical properties of the material being drawn so that undesirable distortions in the article being manufactured are avoided.

7 Claims, 7 Drawing Figures Patented April 4, 1972 4 Sheets-Sheet 2 a WEN '1 (J/ 5 WILLIAM H. CLENDENIN BY )Z oms B. P

fiUM/ER ATTORNEYS Patented April 4, 1972 3,653,301

4 Sheets-Sheet 3 FIG.4

66 IN VEN TORS WILLIAM H. CLENDENIN THOMAS B. P UMIER ATTORNEYS Patented April 4, 1972 4 Sheets-Sheet 4.

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ATTORNEYS DRAWING PRESS PRESSURE CONTROL BACKGROUND OF THE INVENTION This invention relates to a drawing press mechanism used primarily for forming cans, shells and the like out of sheet material. More particularly, this invention relates to an apparatus which adjustably controls the resistance furnished by the pressure pad in a drawing press.

In the drawing of sheet material into articles such as cans, it is important to avoid distortions such as buckling or wrinkling of the material as it is being drawn and shaped over a die. When working with standard metal alloys and standard shaped, relatively simple dies, past mechanisms have been able to avoid such wrinkling merely by providing a variable resistance force to the drawing stroke of the press. Thus prior presses provided the largest required resistance at the beginning of each drawing stroke, the amount of force required being different for each type of material. Due to this inflexibility in the design, the amount of resistance was reduced as the stroke continued. This approach often necessitated a differently designed resistance mechanism for each material drawn and did not result in a consistent application of resistance pressure.

With the advent of the use of aluminum for many items which were previously drawn from tinplate or other alloys, and particularly with the advent of aluminum alloys such as the H19 alloy, it became necessary to give serious consideration to the variable range between yield and tensile strengths resultant from standard mill specifications, percentage of elongation, formability, and variable directional properties. Consideration of these factors rendered the aforementioned resistance controls unsatisfactory.

Modern aluminum alloys have therefore rendered the control systems of the past obsolete in that small variances in metal thickness or gauge, tensile strength, yield strength, percent of elongation, formability, and directional properties, as well as small variances in the configuration of the can or object to be drawn, now require a novel type of control system, particularly one which can readily be adjusted to compensate for these variances.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide a novel pressure control device for a drawing press which prevents distortions in the material being drawn.

It is another object of the present invention to provide a device, as above, which is readily adjustable so that the drawing press can operate on all types of sheet materials, including those alloys such as H19 aluminum as well as non-metallic sheet materials and including those having variations in yield strength, tensile strength, percent elongation, formability, and directional properties.

It is still another object of the present invention to provide a device, as above, which will prevent buckling or wrinkling distortions in a wide variety of die shapes and configurations.

' piston. The second piston will usuallyhave a large working It is a further object of the present invention to provide a device, as above, which is readily adjustable so that one drawing press can be used for a variety of sheet material gauges.

These and other objects which will become apparent from the following specification are accomplished by structures hereinafter described and claimed.

In general, a standard drawing press is provided with a resistance pressure control which capitalizes on the speed of the ram and subsequent force created at the collision point so that the necessary large initial resistance pressure is provided. This pressure, however, is less than that of prior presses. Then after a certain adjustable delay, a greater amount of resistive force to replace that provided by the ram speed is created. The initial force of the stroke is resisted by a first piston in a cylinder, the first piston presenting a small area upon which fluid pressure is allowed to work to provide only the increment of force (combined with the ram force) necessary to start the draw. As the force created by the ram speed decreases and the small area and present, therefore, a much larger resistive force. The remainder of the drawing stroke is then resisted by the total force acting against both pistons. The space between the pistons can be adjusted so that the duration of the small resistance can be regulated and further adjustment of the pressure may be made by varying the speed of the ram itself.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially broken away cross section of a standard drawing press having a pressure control mechanism according to the present invention and shown at the beginning of the drawing stroke.

FIG. 2 is a partially broken away cross section sequentially following FIG. 1 showing the drawing press in a position just after the beginning of the drawing stroke.

FIG. 3 is an enlarged cross section of the blank and draw tooling portion of the device as shown in FIG. 2.

FIG. 4 is a partially broken away cross section sequentially following FIG. 2 showing the drawing press in a position substantially at the end of the drawing stroke.

FIG. 5 is a partially broken away cross section of the standard drawing press having a pressure control mechanism according to the present invention and shown in a position after the beginning of the retracting stroke sequentially following FIG. 4.

FIG. 6 is a partially broken away cross section sequentially following FIG. 5 showing the drawing press in a position substantially at the end of the retracting stroke.

FIG. 7 is a sectional view taken substantially along line 77 of FIG].

DESCRIPTION OF THE PREFERRED EMBODIMENT A drawing press mechanism according to the present invention is indicated generally by the numeral 10 and is shown as having an annular press bed 11 which carries a bolster plate 12. A die holder 13 is carried by the bolster plate 12 and is provided in the top thereof, with two circular concentric recesses 14 and 15. Recess 14 is adapted to receive the annular die ring 16, while recess 15 is adapted to receive the lower end of the die block or anvil 17. Extending upward through the bolster 12 and die holder 13, and into the voided area between the die 17 and die ring 16, are two pressure pins 18. Resting atop pins 18 is the annular pressure pad 19 having an annular flange or lip 20 which rests against the shoulder 21 formed in die ring 16. It is evident that the axial height of the die ring 16 in recess 14 plus the height of the die holder 13 and bolster l2 equals the axial height of the pressure pad 19 and pins 18, as well as the height of the die 17 in recess 15 plus the die holder 13 and bolster 12, so that a flat bed or surface is provided for the passage of the stock of continuous sheet material or blank B.

A press slide plate 30 carries an annular punch holder 31 which has recesses 32 therein receiving the head of positioning bolts 33. Bolts 33 carry a stock stripping ring 34 which remains biased toward the blank B by springs 35. Centrally of the annular punch holder 31 in a circular recess 36 into which an annular die ring 37 is received. Die ring 37 has an annular shoulder 38 for engaging an inner die member 39.

Extending downwardly through slide plate 30 and punch holder 31 is a rod 40 which has a profile pad 41 at its lower end. Rod 40 is normally held in the raised position by a spring 42 telescopically received around the upper end of rod 40 between a flange 43 and plate 30.

The upper inner surface of the annular punch holder 31 is provided with threads 44 which receive spring adjusting nut 45. Nut 45 regulates the bias provided by disc spring 46 which serves to maintain the inner die member 39 flush on shoulder 38 and profile pad 41.

The drawing press mechanism hereinbefore described is a standard item such as that sold by The Minster Machine Company, Minster, Ohio. As such, said construction has been described only in general terms, the'details of the press being unimportant to the basic concept of the present invention.

Received within the opening in the annular press bed 11 is the pressure cushioning control device indicated generally by the numeral 50. The pressure control 50 consists of a first cylinder housing 51 having a piston 52 which is somewhat cup-shaped in cross-section having a base portion 53 and upright side portions 54. The top of each side 54 is in contact with the lower end of each pressure pin 18 of press 10. Near the top of piston 52 is a radially extending annular flange 55 which provides the relatively small working surface 56 as will hereinafter be described. The base 53 of piston 52 is received through the ring-like portion 57 of cylinder housing 51 and into a dead air chamber 58 within a second cylinder housing 59. Thus portion 57 provides a common wall between cylinders 51 and 59. While it is evident that one skilled in the art could provide one integral housing for both pistons, individual first and second cylinder housings 51 and 59-are shown. and are attached to each other and to the bolster 12 as by a plurality of bolts 60. Of course, whether one or two cylinder housings are presented, it is evident that the chambers for each piston must be separate.

The second cylinder housing 59 contains a T-shaped (in cross-section) piston 61 with the top portion 62 extending between the walls of the housing 59 and communicating on one side with chamber 58 and on the other side with air chamber 63. The base of the T-shaped piston 61 is threaded at its lower end and extends through the bottom wall 64 of housing 59. The initial position of piston 61 within housing 59 and thus the size of chamber 58 and the amount of movement of piston 61 is adjustable as by adjusting nuts 65.

A source offiuid under pressure (not shown) communicates with chamber 63 of cylinder 59 through hose 66 which is threaded into bottom wall 64. Further, the fluid under pressure is put in contact with the working surface 56 via conduit 67 which extends internally of the walls of cylinder housings 59 and 51. It is contemplated herein that the fluid being utilizcd is air under pressure. However, it is evident that the device described herein could be readily adapted for use with oil or other hydraulic fluid.

The operation of this device will now be described in detail. As shown in FIG. 1, the press is in its inactive state with air pressure acting in chamber 63 against piston 61 (the adjusting nut 65 having been positioned as desired) and also through conduit 67 into the first cylinder 51 against surface 56. In this position, the slide plate 30 and its associated members are-at the uppermost extent of their movement and the blank B is in position to be cut and drawn into a finished product. In the environment depicted, the product being manufactured is a small specialty foodstuff can having the configuration as shown by the mating faces of the die 17 and profile pad 41. This type of object is displayed herein merely as a typical example, it being understood that the principle described herein relates to controlling the resistance pressure no matter what the configuration of the object being drawn. However, the shape shown is one which has proved particularly difficult to draw in the prior art structures discussed in that buckling or wrinkling in and around the contours of the profile pad 41 was prevalent.

As the slide plate 30 begins its downward movement, being driven by a standard press motor (not shown), the die ring 37 cuts the blank B and'the inner die member 39 begins drawing the blank along the die 17. This downward movement, shown in FIG. 2, is initially yieldingly resisted only by the fluid pressure acting against surface 56 of piston 52, the force being transmitted through pins 18, and thus the blank is quickly and cleanly sheared with buckling in the area indicated generally At the position shown in FIG. 2, the piston 61 has not yet moved, piston 52 having just come into contact therewith. However, further downward travel of the-plate 30 to continue drawing the blank B over the die 17 is resisted by the fluid pressure against both pistons 52 and 61, piston 61 having a larger area exposed to the fluid pressure and therefore increasing the resistive force. Thus at the end of the drawing stroke shown in FIG. 4, the adjusting nuts 65 have. moved with piston 61 and are shown moved away from bottom wall 64. This increase in resistance to the downward stroke allows the blank to be carefully and slowly drawn into final shape with the pressure being carefully controlled so that the point of tensile strength of the material is only. approached and not surpassed. This is, of course, critical in metals where the tensile and yield points are quite close together.

As the slide plate 30 begins to retract (FIG. 5), the blank, which has now been drawn into a can C, is carried upward by the inner die 39 and pad 41 away from the die 17. This movement is toward the knock out bar 48 which, as shown in FIG. 6, is contacted by rod 40 causing the profile pad 41 to push the can C out from within the inner die 39. The air entrapped in chamber 69 defined by flange 55 is allowed to escape through vent 70. 7

Throughout the drawing stroke the pressure on pistons 52 and 61 can be carefully controlled, dependent on the specific tensile strength of the specific material being drawn. For example, if working with the H19 aluminum alloy which can have a range of tensile strengths from 33,000 to 42,000 pounds, it has been found that a corresponding range of 2,320 to 4,480 pounds of force exerted by piston 52 is sufficient and a corresponding range of 5,360 to 7,520 pounds of force exerted by both pistons 52 and 61 when working together is sufficient. On the other hand, if the present device is being utilized to draw an ABS plastic sheet which has a range in tensile strength from 1,540 to 1,840 pounds, it has been found that a corresponding range of 480 to 1,340 pounds of force exerted by piston 52 is sufficient and a corresponding range of 1,450

to 3,350 pounds of force exerted by both pistons 52 and 61 when working together is sufficient.

It should now be evident that the device described herein provides a highly accurate and highly adjustable resistive force to the drawing stroke of the press. The primary adjustment ispistons to provide an even finer control. From the above description one skilled in the art should readily be able to determine these adjustment parameters so that precise drawing procedures can be carried out, thus substantially improving the drawing art.

We claim:

1. Apparatus for controlling the resistance to the downward stroke of a drawing press mechanism comprising, a first cylinder, a second cylinder aligned therewith, said first and second cylinders having a common wall between them, first piston means movable within said first cylinder, second piston means movable within said second cylinder, said first and second cylinder receiving fluid under pressure and means moving said first piston means responsive to the initial downward movement of the press against the fluid pressure in said first cylinder, said first piston means thereafter extending through said common wall to contact said second piston means, said second piston means being responsive to the movement of said first piston means so that continued movement of the press is resisted by fluid pressure acting against said first and second piston means.

2. Apparatus according to claim 1 having means to adjust the position of said second piston means relative to said first piston means.

piston means is in the range of 2,320 to 4,480 pounds and theexposed area of said first and second piston means is such that the total force on said first and second piston means is in the range of 5,360 to 7,520 pounds to draw an H19 aluminum alloy having a tensile strength in the range of 33,000 to 42,000

pounds.

6. Apparatus according to claim 3 wherein the exposed area of said first piston means is such that the force on said first piston means is in therange of 480 to 1,340 pounds and the exposed area of'said first and second piston means is such that the total force on said first and second piston means is in the range of 1,450 to 3,350 pounds to draw an ABS plastic material having a tensile strength in the range of 1,540 to 1,840

pounds.

6. Apparatus according to claim 1 wherein said second piston means is adjustably movable toward and away from said first piston means.

i l 1' I 

1. Apparatus for controlling the resistance to the downward stroke of a drawing press mechanism comprising, a first cylinder, a second cylinder aligned therewith, said first and second cylinders having a common wall between them, first piston means movable within said first cylinder, second piston means movable within said second cylinder, said first and second cylinder receiving fluid under pressure and means moving said first piston means responsive to the initial downward movement of the press against the fluid pressure in said first cylinder, said first piston means thereafter extending through said common wall to contact said second piston means, said second piston means being responsive to the movement of said first piston means so that continued movement of the press is resisted by fluid pressure acting against said first and second piston means.
 2. Apparatus according to claim 1 having means to adjust the position of said second piston means relative to said first piston means.
 3. Apparatus according to claim 1 including means to provide a fluid under pressure to both said first and second piston means within said first and second cylinders.
 4. Apparatus according to claim 3 wherein said second piston means has a larger area exposed to said fluid under pressure than said first piston means.
 5. Apparatus according to claim 3 wherein the exposed area of said first piston means is such that the force on said first piston means is in the range of 2,320 to 4,480 pounds and the exposed area of said first and second piston means is such that the total force on said first and second piston means is in the range of 5,360 to 7,520 pounds to draw an H19 aluminum alloy having a tensile strength in the range of 33,000 to 42,000 pounds.
 6. Apparatus according to claim 3 wherein the exposed area of said first piston means is such that the force on said first piston means is in the range of 480 to 1,340 pounds and the exposed area of said first and second piston means is such that the total force on said first and second piston means is in the range of 1,450 to 3,350 pounds to draw an ABS plastic material having a tensile strength in the range of 1,540 to 1,840 pounds.
 6. Apparatus according to claim 1 wherein said second piston means is adjustably movable toward and away from said first piston means. 